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SubjectRe: [PATCH 1/3] dt-bindings: dmaengine: Add one new cell to present hardware slave id
Hi Arnd,

On Fri, 1 Feb 2019 at 19:53, Baolin Wang <baolin.wang@linaro.org> wrote:
>
> Hi Arnd,
> On Thu, 31 Jan 2019 at 00:52, Arnd Bergmann <arnd@arndb.de> wrote:
> >
> > On Tue, Jan 22, 2019 at 2:21 PM Baolin Wang <baolin.wang@linaro.org> wrote:
> > >
> > > The DMA engine clients can trigger DMA engine automatically by setting
> > > the corresponding hardware slave id for the DMA engine. Thus add one
> > > cell to present the hardware slave id for DMA clients.
> > >
> > > Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
> > > ---
> > > Documentation/devicetree/bindings/dma/sprd-dma.txt | 12 +++++++-----
> > > 1 file changed, 7 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/Documentation/devicetree/bindings/dma/sprd-dma.txt b/Documentation/devicetree/bindings/dma/sprd-dma.txt
> > > index 7a10fea..7812cf0 100644
> > > --- a/Documentation/devicetree/bindings/dma/sprd-dma.txt
> > > +++ b/Documentation/devicetree/bindings/dma/sprd-dma.txt
> > > @@ -6,8 +6,8 @@ Required properties:
> > > - compatible: Should be "sprd,sc9860-dma".
> > > - reg: Should contain DMA registers location and length.
> > > - interrupts: Should contain one interrupt shared by all channel.
> > > -- #dma-cells: must be <1>. Used to represent the number of integer
> > > - cells in the dmas property of client device.
> > > +- #dma-cells: must be <2>. Used to represent the channel id and slave id
> > > + of integer cells in the dmas property of client device.
> > > - #dma-channels : Number of DMA channels supported. Should be 32.
> > > - clock-names: Should contain the clock of the DMA controller.
> > > - clocks: Should contain a clock specifier for each entry in clock-names.
> > > @@ -28,14 +28,16 @@ apdma: dma-controller@20100000 {
> > >
> > > Client:
> > > DMA clients connected to the Spreadtrum DMA controller must use the format
> > > -described in the dma.txt file, using a two-cell specifier for each channel.
> > > -The two cells in order are:
> > > +described in the dma.txt file, using a three-cell specifier for each channel.
> > > +The three cells in order are:
> > > 1. A phandle pointing to the DMA controller.
> > > 2. The channel id.
> > > +3. The hardware slave id which is used for clients to trigger DMA engine
> > > +automatically.
> >
> > I notice that this is an incompatible binding change. Is that necessary?
> > If the current code works, I'd suggest allowing both #dma-cells=<2>
> > and <3>, and then implementing both in the driver.
>
> Yes, this is necessary.
>
> Yes, current code can work, but the problem is that the DMA clients
> must add one property (something like "sprd,slave-id") to specify the
> slave id. So considering this, we want to change the dma-cells to 2,
> including dma channel and dma slave id, which can avoid introducing
> some similar properties for DMA clients.
>
> Now there are no DMA clients in mainline for Spreadtrum platform, and
> we want to upstream our first DMA clients: SPI controller. So no other
> drivers need to change when we changing dma cells. Thanks.

Do you have any other concerns about this patch set? If not, I think
Vinod can apply this patch set. Thanks.

--
Baolin Wang
Best Regards

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